Radio-based systems for traffic sign recognition are state of the art. A traffic sign transmits its meaning and, if appropriate, its position by radio to a radio receiver within the vehicle.
An alternative approach to traffic sign recognition has already been implemented in production vehicles. Traffic signs are recognized by means of a camera sensor system within the vehicle. Such systems can be supported by a navigation system including an electronic map. Traffic sign recognition (TSR) by means of a camera system is based on two essential steps. Step 1 is the search for circular structures (e.g. speed limits) or rectangular structures (e.g. town signs). When suitable candidates have been detected, they are then classified in a subsequent step. For example, numbers are identified using pattern recognition.